1. Field of the Invention
The present invention relates generally to threaded end couplings and more specifically, but not exclusively, to end couplings for rock bolts and rock bolt assemblies incorporating such end couplings.
2. Description of Related Art
Roof and wall support is vital in mining and tunnelling operations. Mine and tunnel walls and roofs consist of rock strata, which must be reinforced to prevent the possibility of collapse. Rock bolts are widely used for consolidating the rock strata.
In conventional strata support systems, a bore is drilled into the rock by a drill rod, which is then removed and a rock bolt is then installed in the drilled hole and secured in place typically using a resin or cement based grout. The rock bolt is tensioned which allows consolidation of the strata by placing that strata in compression. The rock bolt is typically formed from a steel rod.
To allow the rock bolt to be tensioned, the end of the bolt may be anchored mechanically to the rock formation by engagement of an expansion assembly on the end of bolt with the rock formation. Alternatively, the bolt may be adhesively bonded to the rock formation with a resin bonding material inserted into the bore hole. Alternatively, a combination of mechanical anchoring and resin bonding can be employed by using both an expansion assembly and resin bonding material.
In some environments it is preferable that there is no tail protruding from the rock face. This is problematic as it makes it difficult to rotate the installed bolt to effect adequate mixing of the resin or grout and to subsequently tension the bolt once the resin/grout has set.